1. Field
The present application relates generally to light emitting diodes, and more particularly, to a phosphor deposition system to form encapsulations for light emitting diodes.
2. Background
A light emitting diode (LED) is a semiconductor material impregnated, or doped, with impurities. These impurities add “electrons” and “holes” to the semiconductor, which can move in the material relatively freely. Depending on the kind of impurity, a doped region of the semiconductor can have predominantly electrons or holes, and is referred to either as an n-type or p-type semiconductor region, respectively. In LED applications, the semiconductor includes an n-type semiconductor region and a p-type semiconductor region. A reverse electric field is created at the junction between the two regions, which cause the electrons and holes to move away from the junction to form an active region. When a forward voltage sufficient to overcome the reverse electric field is applied across the p-n junction, electrons and holes are forced into the active region and combine. When electrons combine with holes, they fall to lower energy levels and release energy in the form of light.
During operation, a forward voltage is applied across the p-n junction through a pair of electrodes. The electrodes are formed on the semiconductor material with a p-electrode formed on the p-type semiconductor region and an n-electrode formed on the n-type semiconductor region. Each electrode includes a wire bond pad that allows an external voltage to be applied to the LED.
Generally, an LED device comprises an LED chip (or die) that is mounted onto a substrate and encapsulated with an encapsulation material, such as phosphor. The encapsulation operates to protect the LED chip and to extract light. Typically, the LED chip sits in a cavity, which is then filled with the encapsulation material. For LED chips mounted on flat substrates (e.g. Chip on board), there is no cavity and the procedure has to be different. To provide for an encapsulation having a specific geometric shape, an encapsulation mold having the desired geometric shape is separately designed and manufactured. The mold is then mounted onto the substrate so that it fits around the LED chip. The mold is then filled with the phosphor mixture or other encapsulation material.
Unfortunately, using a separately designed and manufactured mold is costly, time consuming, and requires additional manufacturing operations. For example, the mold needs to be designed and fabricated as a separate part, which is time consuming and costly. The mold then needs to be mounted onto the substrate before it can be filled with the encapsulation material, which requires additional manufacturing operations.
Accordingly, there is a need in the art for improvements in encapsulation technology so that encapsulations having a variety of shapes can be formed quickly and flexibility to reduce costs and simplify the manufacture of LED devices.